1. Field of the Invention
The invention is related to the field of wireless networks and, in particular, to determining if subscribers on a call are in a local calling area (LCA) to provide a local or long distance rating for the call.
2. Statement of the Problem
Service providers rate prepaid and postpaid calls in wireless networks based on the locations of a called subscriber. The ratings are typically based on Local Calling Areas (LCA) defined by the service providers. The service providers map out particular geographic areas into calling areas, and define which of the calling areas are home Local Calling Areas (LCA) for particular subscribers. If a called subscriber is in their home LCA, then the incoming call comprises a local call and is billed accordingly. If the called subscriber is not in their home LCA, then the incoming call comprises a roaming call and is billed accordingly.
One problem for service providers is efficiently determining whether the call is a local call in the wireless network (i.e., the called subscriber is in their home LCA). When a subscriber registers with the wireless network, the subscriber is served by a cell site and a Mobile Switching Center (MSC) in a particular LCA. If a call is placed to the subscriber, the signaling for the call typically includes identifiers for the MSC, the cell site, and the sector that are serving the subscriber. For example, in a CDMA network using ISUP signaling, IS-826 triggers include a plurality of parameters, such as an MSCID and an SCELLID. The MSCID is an identifier for the MSC serving the subscriber. The SCELLID (Serving Cell ID) is an identifier for the cell site and the sector serving the subscriber.
The combination of the MSCID and SCELLID, referred to herein as the MSC/cellsiteID, may be used to identify in which LCA a subscriber is located. Service providers generate mapping tables having entries that map an LCA ID to an MSC/cellsiteID. The MSC/cellsiteID is mapped to the LCA ID in that the MSC, the cell site, and the sector identified by the MSC/cellsiteID serve the particular LCA identified by the LCA ID. The mapping tables may then be used to determine if a subscriber is located in a particular LCA based on the MSC/cellsiteID of the MSC, the cell site, and the sector presently serving the subscriber. The LCA corresponding with the present location of the subscriber may be compared against a subscriber profile to determine if the subscriber is in their home LCA.
LCAs frequently overlap meaning that a cell site is located in more than one LCA. FIG. 1 illustrates overlapping LCAs in the prior art. FIG. 1 shows three LCAs: LCA1, LCA2, and LCA3. FIG. 1 also shows three cell sites. Cell site A is located in LCA1. Cell site B is located in LCA1 and LCA2. Cell site C is located in LCA1, LCA2, and LCA3. Cell sites A-C are connected to an MSC that is not shown in FIG. 1.
Assume for discussion that an MSCID for the MSC (not shown) connected to cell sites A-C is “0111111”. Further assume that the SCELLID for Cell site A is “777”, the SCELLID for Cell site B is “888”, and the SCELLID for Cell site C is “999”. Each cell site includes three sectors that have an identifier of “01”, “02”, and “03”, respectively. Thus, an exemplary MSC/cellsiteID for Cell site A may be “011111101777”. The actual format of the MSC/cellsiteID may depend on the type of the MSC. For instance, different MSC vendors may format the MSC/cellsiteID differently.
FIG. 2 illustrates a mapping table in the prior art. As previously stated, entries in the mapping table include an LCA ID mapped to an MSC/cellsiteID. For instance, the first entry in the mapping table includes a LCA ID of “1” mapped to an MSC/cellsiteID of “011111101777”. The first entry means that MSC “0111111”, sector “01”, and cell site “777” are located in LCA1. Similarly, the second entry in the mapping table includes a LCA ID of “1” mapped to an MSC/cellsiteID of “011111102777”. The second entry means that MSC “0111111”, sector “02”, and cell site “777” are located in LCA1.
If a cell site is in multiple LCAs, then there is an individual entry in the mapping table for the MSC/cellsiteID of the cell site and the associated LCA wherein the cell site is located. For instance, for the MSC/cellsiteID “011111101999”, there is an individual entry for LCA1, LCA2, and LCA3 (see FIG. 2). Also, because each cell site has three sectors, the mapping table in FIG. 2 includes an individual entry for each sector.
In a typical wireless network, if a call is placed from a calling subscriber to a called subscriber, an MSC in the wireless network receives the call. To provide charging for the incoming call, a Service Control Point (SCP) or a billing system determines whether the call is a local call or a long distance call. For tills determination, the MSC receives the MSC/cellsiteID for the network resources serving the called subscriber and transmits a report to the SCP that includes the MSC/cellsiteID. The SCP then searches the mapping table with the MSC/cellsiteID for the called subscriber to identify an LCA for the called subscriber. The SCP searches for each instance of the MSC/cellsiteID in the mapping table. The mapping table will include at least three instances of the MSC/cellsiteID representing the different sectors of a cell site. If a cell site is in multiple LCAs, then the mapping table will also include multiple instances MSC/cellsiteID for each of the LCAs. After the SCP locates each LCA for the called subscriber, the SCP compares the LCAs to a subscriber profile for the called subscriber. If one or more of the LCAs match the LCA(s) indicated in the subscriber profile, then the called subscriber is in the home LCA and the call is a local call. Otherwise, the call is a roaming call or long distance call.
Unfortunately, identifying local calls according to the present methods is inefficient. Presently, the SCP has to search the mapping table numerous times to determine the LCA(s) of the called subscriber. This can especially be a problem if the number of entries in the mapping table grows very large due to the overlapping of cell sites in multiple LCAs, due to entries for each sector of a cell, etc. The large size of the mapping table also makes maintenance of the mapping table more complicated. Adding a new cell site to the wireless network also requires that multiple entries be added to the mapping table, which is time consuming. Further, wireless networks may install MSCs from different vendors that define different formats for the MSC/cellsiteID. This further complicates how the entries in the mapping table are populated and how the mapping table is searched. A problem thus remains how to efficiently determine whether calls in a wireless network are in a home LCA.